The present invention relates to a numerical control system. More particularly, the invention relates to a numerical control system which provides power control of a machine tool with programs.
Usually, a numerical control system consists of a numerical control unit, a machine tool, and a power control panel which is installed between the numerical control unit and the machine tool for power control of the machine tool. Control signals are sent and received between the numerical control unit and the machine tool via the power control panel. The power control panel includes relays.
The miscellaneous function, or M-function, signal designates normal or reverse rotation of the spindle. The speed function, or S-function, signal designates the rotary speed of the spindle. The tool function, or T-function, signal designates tools. These signals are once received by the relays of the power control panel and then converted into specified machine tool control signals according to a sequence previously provided by other relays on the basis of respective signals, and are then supplied to the machine tool.
ON-OFF signals from a limit switch or proximity switch on the machine side, which are sent to the numerical control unit from machine tool, are once received by the relays of the power control panel and are then supplied to the numerical control unit.
In a numerical control system, the hardware for numerical control and power control are perfectly separated. Therefore, for different types of machine tools, machining by numerical control has been provided, corresponding to various types of machine tools, by providing a power control panel suitable for just such machine tool. However, the power control panel of known or existing numerical control systems includes relays, and therefore the power control is likely to create difficulties and troubles and has the disadvantage of difficult maintenance. Furthermore, since a large number of relays are included in the power control panel, a large scale circuit or system must be provided with complicated wiring and at high cost. It would therefore be desirable to provide power control with software instead of with hardware such as relays.
The principal object of the invention is to provide a numerical control system which overcomes the problems and disadvantages of known numerical control systems.
An object of the invention is to provide a numerical control system which utilizes software to provide power control by using control programs instead of hardware utilizing relays.
Another object of the invention is to provide a numerical control system which utilizes software to provide numerical control and power control and the software of the numerical control is separated from the software of the power control.
Still another object of the invention is to provide a numerical control system capable of controlling a machine tool by changing only the software for power control without changing the software for numerical control when the machine tool to be controlled is changed.
Yet another object of the invention is to provide a numerical control system having a single central processing unit and an interruption signal generating circuit and which provides numerical control and power control by controlling the central processing unit on a time division basis via an interruption signal generated by the interruption signal generating circuit.